Skin sodium measurement using bioimpedance

Abstract

A technique for determining skin sodium content using bioimpedance spectroscopy includes applying a current at a predetermined frequency to skin of a subject, measuring a voltage across the skin of the subject produced by the current, determining a resistance across the skin of the subject at the predetermined frequency using the measured voltage, and determining skin sodium content using the measured voltage.

What is claimed is: 
     
       1. A method for determining skin sodium content using bioimpedance spectroscopy, the method comprising:
 applying a current at a predetermined frequency to skin of a subject; 
 measuring a voltage across the skin of the subject produced by the current; 
 determining a resistance across the skin of the subject at the predetermined frequency using the measured voltage; and 
 determining, using the measured voltage, skin sodium content using a regression model including a formula, SSC=a*ρ SR +b*age+c, where ρ SR  is calculated skin resistivity, and wherein a, b, and c are constant coefficients configured to correlate skin sodium content obtained by sodium-magnetic resonance imaging with skin resistivity obtained by bioimpedance spectroscopy. 
 
     
     
       2. The method of  claim 1 , further comprising calculating skin resistivity at the predetermined frequency, wherein the skin sodium content is determined at least in part using the calculated skin resistivity. 
     
     
       3. The method of  claim 2 , wherein the skin resistivity (ρ SR ) is calculated using a formula, ρ SR =R F *A/L, where R F  is the resistance at the predetermined frequency, A is a cross-sectional area of a measurement region of the skin, and L is a distance between electrodes that measured the voltage. 
     
     
       4. The method of  claim 1 , wherein the predetermined frequency is in a range between 1 Hertz (Hz) and 1 megahertz (MHz). 
     
     
       5. The method of  claim 1 , wherein the current is applied to dermis of the subject. 
     
     
       6. The method of  claim 1 , wherein the predetermined frequency is selected to traverse through dermis of the subject. 
     
     
       7. The method of  claim 1 , further comprising:
 altering the predetermined frequency; 
 repeating measurement of the voltage and determining the resistance at the altered frequency to determine a tissue type of the subject; and 
 selecting the altered frequency determined to provide skin resistivity for dermis of the subject. 
 
     
     
       8. The method of  claim 1 , further comprising:
 determining one or more of a conductivity and a dielectric constant for current applied at a plurality of different frequencies; 
 determining a slope for one or more of the conductivity and the dielectric constant between at least two of the plurality of different frequencies; and 
 determining a tissue type using the slope. 
 
     
     
       9. The method of  claim 8 , wherein the tissue type includes one of skin, fat, and muscle, and wherein tissue types of fat and muscle are disregarded for calculating skin sodium content. 
     
     
       10. The method of  claim 8 , wherein the tissue type includes one of epidermis, dermis, and subcutaneous layer, and wherein all tissue types except the dermis are disregarded for calculating skin sodium content. 
     
     
       11. The method of  claim 1 , further comprising associating the skin sodium content with a physiological characteristic to determine a predictive health condition of the subject. 
     
     
       12. The method of  claim 1 , further comprising transmitting data to a computing device, the data including one or more of the predetermined frequency, the voltage, the resistance, skin resistivity, and the skin sodium content. 
     
     
       13. The method of  claim 1 , further comprising measuring extracellular volume (ECV) and intracellular volume (ICV) of the skin. 
     
     
       14. The method of  claim 1 , further comprising:
 continuously calculating skin sodium content for a predetermined time period; and 
 transmitting a notification when skin sodium content is outside of a predetermined range.